Back Injury!

Just a heads-up (no pun intended) to those of you doing this. You MUST, MUST, MUST loosen up beforehand. I heard a loud POP in my back one time (I almost had the whole shaft in and strained for the last half-inch), and I suffered so long in pain that I have never done it again. It's been about a year since, and I might try again but with much loosening up first. Wish me luck, and BE CAREFUL!